Re: Bastnaesite
Generally speaking, the term "bastnaesite" denotes a group of minerals which can be regarded as being comprised of fluorocarbonates of certain rare earth metals. However, the nomenclature used to describe such materials is often rather vague. For example, since the chief components of bastnaesite are the "rare earths" such materials are sometimes referred to as rare earth oxides. These materials also are commonly referred to as "lanthanides". This term is obviously a corruption of the word lanthanum, which of course is the first member (or lowest atomic number member) of the lanthanide group in the periodic table. Those familiar with this art also will appreciate that it is not at all an uncommon practice to use the symbol for the lanthanides ("Ln") to generally denote all of the lanthanides when they are considered as a group. Similarly, it also is common practice to refer to the various oxides of the entire lanthanide group as LnO--and to their oxyflourides as LnOF. Given all of these considerations, it is quite common to designate the chemical makeup of bastnaesites, in general, by the formula: (Ce,La)OF, even though such materials contain many other elements. For example, mineral bastnaesite contains from about 65 to about 80% by weight of assorted rare earth elements (calculated as rare earth oxides) with its primary metallic components being lanthanum and cerium. This fact explains the widespread use of (Ce,La)OF as the chemical formula for these materials. However, bastnaesite minerals almost always contain small proportions of various other rare earth elements such as praseodymium, neodymium, samarium, europium, and gadolinium. For example, chemical analysis of a typical bastnaesite mineral might show proportions of individual rare earth elements (calculated as oxides) to the total rare earth elements (also calculated as oxides) which fall within the general ranges: 45 to 55 wt. % CeO.sub.2, 29 to 35 wt. % La.sub.2 O.sub.3, 11 to 15 wt. % Nd.sub.2 O.sub.3, 2.5 to 5.5 wt. % Pr.sub.2 O.sub.3, 0.3 to 0.7 wt. % Sm.sub.2 O.sub.3, 0.1 to 0.3 wt. % Gd.sub.2 O.sub.3, 0.05 to 0.15 wt. % Eu.sub.2 O.sub.3 and 0.05 to 0.35 wt. % of other rare earth elements.
Next, it should be noted that bastnaesite is a somewhat chemically reactive mineral. Consequently, it can be modified by relatively moderate chemical and/or physical treatment processes such as steaming, calcining and acid leaching. For instance, when naturally occurring bastnaesite is calcined in air at a temperature around 700.degree. C., it undergoes a chemical reaction wherein some of its rare earth fluoro-carbonates are converted to rare earth oxyfluorides. By way of another example of such modifications, mineral bastnaesite can be leached with certain strong acids in order to withdraw its strontium and barium content. Be all of this as it may, this invention contemplates use of either naturally occurring forms of bastnaesite or any number of chemically and/or physically treated forms of that mineral. Hence, for the purposes of this patent disclosure, the terms "bastnaesite" "treated bastnaesite" "bastnaesite mineral(s)", "bastnaesite-like materials" etc. should be taken to include not only those raw mineral forms of bastnaesite found in nature, but also a wide variety of physically or chemically treated forms of bastnaesite minerals--indeed, for the purposes of this patent disclosure, these terms should even be taken to include any synthetic material having a distribution of rare earth elements to total rare earth elements substantially similar to those of naturally occurring bastnaesite minerals.